DIAGRAM OF HUMAN HEART WITH EXPLANATION

The heart is roughly triangular in shape. It has four compartments called chambers inside it. The upper two chambers of the heart are called atria and the lower two chambers are called ventricles. The atria receive blood from the two main veins. The left atrium is connected to the left ventricle through a valve V1 and the right atrium is connected to the right ventricle through another valve V2. These valves prevent the backflow of blood into atria when the ventricles contract to pump blood out of the heart to the rest of the body because when the ventricles contract, the valves V1 and V2 close automatically so that the blood may not go back into the atria. The job of heart is to pump blood around our body. All the atria and ventricles of the heart contract and relax at appropriate times and make the heart behave like a pump. A sheath of tissue called pericardium protects the muscular heart.

The function of human heart :-

* It is a four chambered structure consisting - the right auricle , the left auricle , right ventricle and left ventricle.

* The Auricles are smaller and placed above the ventricles. Auricles are partitioned by a muscular called septum.

* The right auricle receives the deoxygenated blood from all parts of the body except the lungs. It pumps this blood into the right ventricle. Then , the right ventricle pumps the deoxygenated blood to the lungs. The left auricle receives oxygenated blood from the lungs through pulmonary veins. It pumps this blood into the left ventricle. The left ventricle pumps the oxygenated blood to the distant organs in the body.

* Each auricle communicates with the ventricle of its side by a pore which is guarded by valves. These valves allow the blood to flow from the auricles to the ventricles but check its return to the auricles. Thus , the heart there is a complete separation of oxygenated and deoxygenated blood. The heart is enclosed in a double membrane called pericardium. It contains fluid which protects the heart from any shock or mechanical injury.

*The heart collects blood through both the auricles and then distributes it through ventricles. The action of heart includes contraction and relaxation of the auricles and ventricles.

* A contraction of heart is called systole and diastole. The contraction and relaxation occur in an automatic rhythmic fashion. The auricles and ventricles contract alternately. The rhythmic contraction and relaxation of heart is called a heart beat.